Packages of heat exchanging plates for rotary regenerative heat exchangers



PACKAGES OF HEAT EXCHANGING PLATES FOR ROTARY REGENERATIVE HEAT EXCHANGERS Dec. 17.. 1968 K. OLDEHAVER 3416,596

Filed Aug. 11, 1966 2 Sheets-Sheet 1 INVENTDR K laus Oldc haveR' BY WWW.

ATTORNEY 3,41 6596 FOR ROTARY ERS Dec. 17, 1968 K. OLDEHAVER PACKAGES OF HEAT EXCHANGING PLA REGENERATIVE HEAT EXGHA Flled Aug 11 1966 2 Sheets-Sheet 2 I a I I I l I I I N H N I I uvymbza Klaus OldehaveR- United States Patent 3,416,596 PACKAGES OF HEAT EXCHANGING PLATES FOR ROTARY REGENERATHE HEAT EXCHANGERS Klaus Oldehaver, Leiman, near Heidelberg, Germany, as-

signor to Svenska Rotor Maskiner Aktiebolag, Nacka, Sweden, a corporation of Sweden Filed Aug. 11, 1966, Ser. No. 571,873 Claims priority, application Germany, Aug. 12, 1965,

56,865 Claims. (Cl. 16510) ABSTRACT OF THE DISCLOSURE A framed structure is provided for holding packages of heat exchanging plates and for easy insertion and withdrawal of said packages into and out of a rotary regenerative heat exchanger with said framed structure being substantially open on all sides and constructed to provide as little interference as possible with the fiow of heat exchange fluid through said exchanger. The structure includes two spaced-apart substantially open frames interconnected with a plurality of substantially flat stays with the latter being positioned so that the longer sides of their cross-section are parallel with the flow of the heat exchange fluids. In addition, as disposed in an exchanger With a vertical axis, the framed structure has at least one stay on the upper side thereof and more stays on the lower side than the upper side with the lower and upper stays being vertically offset from each other. The frame does not limit the shape of the packages of plates being held which may be either triangular or parallelepipedic and they are so constructed that when disposed in layers in the regenerator body the lower frame structures support the upper ones without special support devices from the regenerator body itself except for the lower layer of packages.

This invention relates to rotary regenerative heat exchangers and more particularly to such heat exchangers in which the heat exchanging mass consists of plates. The invention refers to a package of heat exchanging plates which differs from previously known embodiments of such packages in several advantageous Ways and the package according to the invention is characterized by a frame structure which is composed of two frames contacting the two outermost plates of the package and being interconnected by means of stays.

The invention has for its object to make it possible to increase the density of the mass within the regenerator body and to decrease the time required for inserting the plates in the regenerator body.

The idea to put the plates together in packages and to insert these packages as units in the regenerator body has been known for a long time. Particularly such packages have been used at the cold end of regenerative air preheaters utilizing flue gases as heating fluid since the plates are subjected to the greatest risk of corroding at this end. It is therefore necessary to exchange plates more frequently at the cold end even though for this end are often used enamelled plates in order to increase the service life. The reduction of the time required for the insertion and removal of the plates obtained by using packages results in the important advantage that the air preheater need only be stopped for a short time for such an exchange. Further, the enamelled plates are also protected against mechanical damages by the boxes during the insertion in the regenerator body.

In spite of these advantages the boxes or baskets hitherto used are impaired by substantial drawbacks. Thus, the manufacturing costs are considerable and the weight of the boxes is not insignificant. The space occupied by the boxes involves a loss of space for the heat exchanging plates. A severe draw-back resides in the fact that the flow area for the heat exchanging fluids is reduced by interference from the boxes themselves and this reduction may amount to 20%. This results in an increased loss of pressure as well as a loss of effective surface for the heat exchange. For this reason such box-like packages are normally used only at the cold end while at the hot end the plates are inserted individually. Thus, with respect to the hot end the advantages of the boxes are overcome by the draw-backs mentioned. In U.S.A., however, boxes are used also at the hot end for the sake of simplification and reduction of the assembling costs. The result has not been fully satisfactory due to the abovementioned draw-backs.

The invention gives directions how to maintain the advantages of the known plate boxes while obviating their draw-backs and this result is obtained by means of the frame structures according to the invention.

The invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a plate box of known type and FIG. 2 a similar view of a frame structure according to the invention in which the plate package is indicated by chain dotted lines.

FIG. 3 shows two superimposed frame structures according to the invention, the plate packages being also in this case indicated by chain dotted lines.

The plate box shown in FIG. 1 consists of walls 1, 2, 3 and 4 the upper and lower edges of which are bent at right angles inwardly so that they form holding flanges 1A, 2A, 3A and 4A for the heat exchanging plates. There are holding flanges at the top as well as at the bottom so that the boxes can be turned upside down when the plates become damaged due to corrosion at their cold end portions. In this manner the boxes may be used further until the other end portions are likewise damaged.

The arrangement may 'be such that the boxes can be removed and inserted either in radial or in axial direction for turning or exchange. In the embodiment shown in FIG. 1 is is assumed that the boxes are moved in radial direction and therefore each box is provided with a handle 5.

It is evident that the flanges of the four box walls reduce the free cross-sectional area.

In the package according to the invention this drawback is obviated. The weight and the manufacturing costs of the frame structure are also smaller than those of the box according to FIG. 1.

According to the embodiment shown in FIG. 2 the frame structure according to the invention consists of two frames viz. the front frame 6, 7, 8, 9 and the rear frame 10, 11, 12, 13. These two frames rest against the two outermost plates of the package and are interconnected by stays which pass over the edges of the plates at the inlet and outlet ends of the package. At the top of the package there are two stays 14 and 15 While three stays 16, 17 and 18 are provided at the bottom and carry the weight of the heat exchanging plates.

The assemblage of a package is carried out in the following way. Firstly there is manufactured a preferably welded frame structure which is complete with the exception of the upper stays 14 and 15. The plates are inserted in this upwardly open frame structure so that they form a package as indicated by chain dotted lines. When the frame structure is filled its end frames are bent outwardly under the action of the pressure from the elastic plates but before the attachment of the stays 14 and 15 the upper ends of the frames are pressed towards each other so that the frames become perpendicular to the bottom stays. The stays 14 and 15 may be secured to the frames by means of welding but it is also possible to provide an easily releasea'ble connection.

The plate package thus formed can then be inserted in the regenerator body in the same manner as the known plate boxes. The stays 14 and 15 may be provided with holes for lifting hooks or shackle means attached to a crane cable.

The frame structure shown in FIG. 2 is only an illustrative example of the invention. The form and number of the stays may vary. In case of small packages the two upper stays 14 and '15 may be substituted by a single stay while two stays may be sufiicient at the bottom. In other cases it might naturally be necessary to provide a greater number of stays. When inserting the plates in the frame structure it is important to see to it that the plates in the finished package are pressed towards each other so that they do not later on become loose and movable relatively to each other after having been mounted in the regenerator body.

As shown in the drawing the frame structure is preferably made from fiat iron bars and the longer sides of the cross-section of the bars are substantially parallel with the direction of flow of the heat exchanging fluids. Therefore, the flow area is reduced only slightly and further the upper stays are displaced relative to the lower stays. At the sides of the plate packages there are no throttling members at all.

Due to the fact that the two end frames are made from flat iron bars the vertically extending stays of these frames tends to bulge under the action of the pressure from the plates. This deformation is at least partly eliminated at the mounting of the package in the regenerator body. It has proved suitable to choose the dimensions such that after the insertion of the packages in the regenerator body there is a small remaining bulge which, assists in holding the packages firmly in the regenerator body. However, it is also possible to use bars of high bending resistance so that no noticable bulging occurs.

FIG. 3 shows an air preheater having a vertical axis and in which the lower end is the hot end. In this case there are two superimposed layers of plate packages, viz. a lower layer I at the hot end and an upper layer II. The upper frame structure is similar to that shown in FIG. 2. The lower frame structure which carries a higher weight is provided with six stays 19 at the bottom. The lower horizontal stays 9 and 13 of the end frames of the upper package rest on the inclined stays 6', 7', 10 and 11 of the lower frame structure. The weight of the two superimposed packages I and II is transmitted to the tangential walls 20 of the regenerator body by the stays 19 of the lower frame structure. The stays 19 of the lower frame structure are for this purpose provided with recesses 19 which guarantee a correct position of the packages on brackets or shoulders 21 or the like secured to the lower ends of the tangential walls.

Under certain conditions it is also possible to have the packages supported by the radial partitions. If, for instance, in the embodiment according to FIG. 2 the distance between the lower ends of the two stays 10 and 11 corresponds to the width of the sector at this location these lower stay ends may be placed on suitable supporting members secured to the partitions. It is also possible to dispose the plates radially instead of tangentially as shown in the three figures so that the plates are in known manner parallel with the divider between the sectional compartments. In such case parallelepipedic plate packages form the central portion of the compartment filling while the remaining space is filled with individually mounted plates of successively varying length in accordance with the triangular cross-section of the space. These individual plates may be riveted together, if desired. However, preferably the plates are disposed tangentially since each sectioned compartment can in its entirety be filled with one set of plates at the same time and it is not necessary to provide separate plates which must be inserted separately.

The frame structures according to the invention do not demand much space and they do not appreciably reduce the flow area. Their weight is so low that it might almost be disregarded. Further, the manufacturing costs are also low.

The frame structures according to the invention are in the first place intended to be used at the hot end of an air prcheater in order to get the benefit of the saving of time offered by plate packages used at this end. At the cold end where the risk of corrosion is greater and particularly when the lower end is the cold end of the regenerator the more stable boxes will still be used. Packages according to the invention may, however, be used in such cases where the upper end is the cold end. In such cases the mechanical stresses in the plates as well as in the frame structures are smaller and the exchange of packages at the cold end, where such exchange must be made more frequently due to the stronger corrosion, can readily take place in accordance herewith.

What I claim is:

1. In rotary regenerative heat exchangers, a cylindrical rotor having sector-shaped compartments, each of said compartments having at least one package of heat exchange plates supported in a frame structure said structure comprising two spaced-apart frames with each said frame being positioned to be at opposite ends of a package of plates disposed therebetween adjacent the outermost plates of said package, a plurality of stays interconnecting said frames and extending transversely thereof and positioned to extend over the plate edges of said package at the inlet and outlet sides thereof, and said stays being substantially fiat and positioned with the longer sides of the cross-section thereof being substantially parallel with the direction of flow of heat exchanging fluids therethrough.

2. A frame structure as recited in claim 1, wherein the frames are trapezoidal and their parallel sides lie at the inlet and outlet sides of the package disposed therein and wherein the stays at the outlet side are displaced relative to the stays at the inlet side.

3. A frame structure as recited in claim 2 for use with a heat exchanger having a vertical axis in which at least one of said stays is disposed at the upper side of a package of plates disposed therein, and in which a greater number of said stays than the .upper side is disposed on the lower side thereof.

4. A rotary regenerative heat exchanger having a vertical axis and comprising a regenerator body containing a plurality of superimposed layers of packages according to claim 3, wherein the frame structures of an upper layer rest on the frame structures of the underlying layer.

5. Heat exchanger apparatus as recited in claim 4 which includes an annular shoulder disposed on the wall of said body for supporting the lowest layer of packages.

References Cited UNITED STATES PATENTS 2,122,176 6/1938 Herbeck 5 3,314,472 4/1967 Krumm et a]. 165-10 FOREIGN PATENTS 503,857 4/1939 Great Britain. 1,027,371 2/ 1953 France.

ROBERT A. OLEARY, Primary Examiner.

T. W. STREULE, Assistant Examiner. 

